VOL. LI FEBRUARY No. 2 1958 BRITISH BIRDS THE BIRDS OF TIREE AND COLL By J. MORTON BOYD (Department of Zoology, Glasgow University*) (Plates 18-20) THE islands of Tiree and Coll, Inner Hebrides, lie totally within the vice-county Mid Ebudes (103). Situated between Mull and the Barra Isles, they stretch some 45 miles S.W. into the ocean from Ardnamurchan, the most westerly headland of the Scottish main­ land. Their geographical position, and separate scale maps of each, are shown in Figs. 1, 2 and 3. This work is concerned with records of all species of bird observed, from the earliest literature to the present day, not only on Tiree and Coll, but also on all islands and rocks between and including Eilein Mor, N.E. of Coll, and Skerryvore, S.W. of Tiree. The islands are a low undulating platform of Lewisian gneiss masked extensively by raised beach material and wind-blown sand. The sand deposits are particularly widespread in Tiree and S.W. Coll, but in N.W. Coll there are considerable tracts of bare rock. The terrain rises to its highest point (460 feet) in Ben Hynish, Tiree. The principal ecological divisions of the islands are: (i) an intertidal zone, including extensive beaches of shell-sand inter­ spaced with rocky shores trenched by eroded dykes, and fringed with skerries; (ii) grazed sand-dune systems landward to the shore sand, and moorland altered by salt-spray landward to the rocky shores (the only substantial sea-cliffs are at Ceann a'Mhara, Tiree); (iii) machair or sea-meadow, and cultivated calcareous grassland covering wide tracts of Tiree and S.W. Coll; (iv) grazed moorland of mixed grasses, sedges and heather, covering central areas of both islands; (v) lightly grazed heather moorland, covering parts of the interior of Coll; (vi) fresh-water lochs, streams, ditches and marshes form a web over all other ecological zones from the alkaline to the acid ground, and give rise to small brackish estuaries. The beaches, dunes, machair and cultivation, moorland, *Now Nature Conservancy, Edinburgh. 41 42 BRITISH BIRDS [VOL. LI lochs and ditches are all well brought out in the aerial photographs on plates 18-20. With the exception of a few small plantations of deciduous trees in Coll, and a few trees growing in the lee of croft-houses in Tiree, the islands are almost treeless. Whin and bramble thickets grow locally and provide good cover for birds. The islands are dominated by a S.W. air stream, moist, warm, and with high winds. Gusts of 108 m.p.h. have been recorded. The FIG. I—MAP TO SHOW POSITIONS OF COLL AND TIREE IN RELATION TO BARRA, MULL, AND ARDNAMURCHAN ON THE SCOTTISH MAINLAND temperature range is some 3 degrees Fahrenheit less than the Scottish West Highlands, and 6 degrees Fahrenheit less than the Scottish mainland generally. Snow seldom lies more than a few days in the year, and the soil remains open practically all winter. Hours of sunshine are somewhat similar to those of southern England; in May 1948 Tiree had an average of 10.6 hours of sunshine daily. Outstanding features of the fauna (particularly related to the ecology of the avifauna) are: (i) the abundance of snails, bivalves VOL. LI] THE BIRDS OF TIREE AND COLL 43 and slugs in the calcareous fresh waters and grasslands; (ii) the aggregation °f Ay larvae, ants, beetles and earthworms in cow- pats on all grasslands and moorlands; (iii) the presence of Rabbits (Oryctolagus cuniculus) in Coll, and their absence in Tiree (see notes on the Buzzard and compare plates 18 and 19); (iv) the presence of the Hare (Lepus europaeus), the Long-tailed Field Mouse (Apodemus sylvaticus), the Brown Rat (Rattus norvegicus) FIG. 2—MAP OF THE ISLE OF COLL TO SHOW PRINCIPAL PLACE-NAMES AND THB POSITIONS OF ElLEIN MoR AND GuNNA (cf. Fig. 3) and the Pygmy Shrew (Sorex tninutus); (v) the presence of the Brown Trout (Salmo trutta) and the Three-spined Stickleback (Gasterosteus aculeatus) in fresh waters, and the absence of amphibians and reptiles. The agricultural system in Coll is farming (the major farms are named in Fig. 2), while in Tiree it is crofting (the crofting town­ ships are named in Fig. 3). According to the West Highland Survey (Darling et al., 1955), in 1951 the human population in Coll was 200, and that of Tiree 1,200. Casual mention of the avifauna of these islands is made in the Statistical Account of Scotland (1791-1799), but the first comprehensive record appears in A Vertebrate Fauna of Argyll and the Inner Hebrides (1892), by J. A. Harvie-Brown and T. E. Buckley. This volume stimulated interest, and in 1898 44 BRITISH BIRDS [VOL. LI P. Anderson, the game-keeper of Tiree at that time, published the first separate list of the birds of Tiree, to be followed in 1899 by a supplementary list for both Tiree and Coll, by Lieut.-Col. L. H. Irby. Reports of movements and occurrences of birds in Scotland in 1897 and 1898 (Laidlaw, 1898 and 1899) include information from Tiree and the Skerryvore, and a separate list later appeared for Skerryvore (Tomison, 1907). In 1913 Fio 3—MAP OF THE ISLE OF TIREE TO SHOW PRINCIPAL PLACE-NAMES AND THE POSITION OF GUNNA (cf. Fig. 2) Anderson published his second list for Tiree summarizing over 25 years' observations on that island. Thereafter no lists were published for Tiree, and none for the area till Miss MacDougall's list for Coll in 1938. Miss Baxter and Miss Rintoul, in The Birds of Scotland (1953), brought together much information on Tiree and Coll based mostly on the out-dated literature, and a great deal of this is now supplemented by information acquired mainly in the last 10 years from numerous reliable observers. From time to time since 1892, short notes on the birds of the area have appeared in the Annals of Scottish Natural History and the Scottish Naturalist. The author desires to make the following acknowledgements with thanks. His Grace the Duke of Argyll kindly gave access to the game-record of the Tiree Estate. Lists for Tiree were supplied by H. A. Course, James Fisher, D. Gardner-Medwin, J. Graham, N. Hopkins, N. Mclntyre, J. Murray (Edinburgh VOL. LI] THE BIRDS OF TIREE AND COLL 45 Academy Party, 1954), C. F. Priestley, W. C, Taunton, Iolo Williams, and J. T. D. Wilson. Lists for Coll were supplied by A. G. S. Bryson, W, P. Colyer-Fergusson, J. R. Furse, Miss M. Henderson, C. K. M. Stewart, and A. A. K. Whitehouse. Short notes were supplied by W. K. Richmond and L. A. Urquhart. R. Roddam assisted in recent sea-bird counts. Mrs. W. I. Boyd assisted both in the field and in sifting the literature. Dr. J. W. Campbell kindly sent information originally lodged with the Editors of the Scottish Naturalist. Requests for information, all of which brought response, were published in Bird Study, the Edinburgh Bird Bidletin, and the Glasgow and West of Scotland Bird Bulletin. The notes of the author have been made from some 25 visits to Tiree at all seasons, 1 to Coll in summer, 1 to Skerryvore in summer, and 3 to Gunna, summer, autumn and winter, in the period from June 1952 to June 1957. Many of those visits were made in connection with ecological research in Hebridean soils assisted by a grant from the Nature Conservancy, which made possible countless casual observations on birds. SPECIFIC LIST In this list frequent reference is made to the published works on the birds of Tiree and Coll, particularly those which appeared in 1892, 1898, 1899 and 1913 (see pages 43-44). Since many of the remarks in these publications refer not only to those particular years, but also to the ones preceding them, these dates are placed in brackets in such cases. For each species the treatment follows the same plan: a short phrase summing up the seasons when it is present; a review of the breeding records, from Tiree, Coll and the other islands separately; and, lastly, a similar review of the status during the rest of the year, again with separate treatment where this is needed. BLACK-THROATED DIVER (Gavia arctica).—Present all year. Bred in Coll 1899, but no breeding record from Tiree. Mature birds seen regularly April to July off both islands 1954-55, but no recent breeding record or report from fresh waters. GREAT NORTHERN DIVER (Gavia immer).—August to May. No breeding record. Seen off-shore since September 1888 ; November to April 1903-06 at Skerryvore ; similarly 1952-55 off Tiree and Coll. No report from fresh waters. RED-THROATED DIVER (Gavia stellaia).—Present all year. Bred in Coll before 1899 ; bred there 1937-38 ; 8 pairs with young July 1939 ; present August 1945 ; June 1946, 1949 ; May 1954 ; April, June 1955 ; increasing 1956 (W.P.C.-F.). No breeding record from Tiree, and has only twice been reported from fresh waters. Seen off Tiree, September 1956. GREAT CRESTED GREBE (Podiceps cristatus).—January to June. No breeding record. Seen in Tiree January 1891 ; 2 pairs in breeding plumage 22nd May 1900 ; 1 pair May-June 1952. No record from Coll. RED-NECKED GREBE (Podiceps gfheigena).—Spring. Reported from Tiree as common and not breeding (J.T.D.W.). No record from Coll. 46 BRITISH BIRDS [VOL. LI SLAVONIAN GREBE (Podiceps auritus).—October to April. No breeding record. One shot in Tiree 7th November 1888 ; seen there 29th October 1898 ; common there (1913) ; seen Soa Sound 7th April 1954. No record from Coll.